1. Field of the Invention
The present invention relates to an ink jet print head which includes a fluid passage forming substrate having pressure generating chambers formed by anisotropically etching a silicon monocrystalline substrate.
2. Prior Art Discussion
A conventional ink jet print head is shown in FIG. 9. As shown, the print head has a layered structure which is made up of a fluid passage forming substrate 51, a covering member 55, and an elastic plate 57. The fluid passage forming substrate 51 includes a pressure generating chamber 50 that receives an external pressure. The covering member 55 has a discharge orifice 54 communicating with the pressure generating chamber 50 and an ink supplying port 53 communicatively connecting a reservoir 52 to the pressure generating chamber 50. The elastic plate 57 has a pressure generating means 56 and covers one of the major sides of the fluid passage forming substrate 51. The pressure generating chamber 50 is expanded and contracted by the pressure generating means 56 of the elastic plate 57. When expanded, the pressure generating chamber sucks ink from the reservoir 52 through the ink supplying port 53. When contracted, the pressure generating chamber causes the sucked ink to eject outside in the form of ink droplets through the discharge orifice 54.
In forming the fluid passage forming substrate 51 having the pressure generating chambers 50 formed therein, an etching pattern corresponding to an array of pressure generating chambers is formed on a silicon monocrystalline substrate having a face (110). Then, the structure is etched in an alkaline water solution containing potassium hydroxide by an anisotropical etching process. In the process of anisotropically etching the silicon monocrystalline substrate, recesses and openings having (111) faces that are vertical to the (110) face are linearly formed. The recesses and the openings are considerably high in their aspect ratio. The result is the formation of pressure generating chambers arrayed at extremely high density.
In the silicon monocrystalline substrate having a (110) face, (111) faces appear, which are each slanted at about 35.degree. with respect to the surface of the silicon monocrystalline substrate, and extended from the intersection of linear patterns along the (111) faces vertical to the (110) faces. These faces (111) form the walls 58 and 58' of each pressure generating chamber 50.
With the formation of the slanted walls, acutely angled spaces 59 and 59' are formed in the vicinity of discharge orifices 54 and ink supplying ports 53. In the spaces, ink stagnates and air bubbles stay there. The air bubbles staying there are hard to remove.